The invention relates to a screen consisting of a supporting frame on whose upper side mutually adjoining, apertured screen elements of resilient material with substantially rectangular borders are detachably attached.
The apertured screen elements of resilient material are primarily to serve as wear-resistant screen means proper, but also have the task of protecting the supporting frame against the wear caused by the material treated by the screen.
However, the screen elements are nevertheless worn or otherwise damaged over an extending period of time, e.g. by falling screen material, and must therefore be replaceable.
The Norwegian Published Application No. 142 943 discloses a screen of the type mentioned above, in which the replaceable screen elements are attached to the supporting frame by means of stud-shaped fasteners. This technique is vitiated by the drawback that it requires the use of a very large number of fasteners, which can easily be lost and which can spring up when the frame is deflected. Moreover, the fasteners are damaged more or less when the screen elements are replaced.
Screens have been developed in which the fasteners are integral parts of the screen elements. However, this involves a very complicated manufacturing process which adds to the manufacturing costs of the screen elements. The integral fasteners moreover break when the individual screen elements are replaced. The resulting bottom frame becomes heavy, which reduces the vibration capacity of the machine.
The Federal Republic of Germany Utility Model No. 7 838 335 discloses a further development of a screen where the screen elements are attached by means of fasteners, which are firmly connected to a supporting structure. These fasteners are rectilinear, specially made metal profiles with an upwardly open U-shaped cross-section, whose free forks are extended at the top and lockingly engage longitudinal notches in the edges of their respective one of two adjoining screen elements. Thus, the screen elements are only supported at their longitudinal edges as there is no supporting frame, and the load capacity of the screen is therefore not fully satisfactory.
Another known screen comprises a supporting frame of woven, specially made profile wires which are disposed perpendicularly to one another and to which rubber screen elements are attached, the screen elements being provided along all their edges with downwardly open grooves which can be clamped onto the wire net. The wire net cannot carry large loads without being deflected, and this construction is therefore not capable of supporting the screen elements to a satisfactory degree either. The rubber in the screen elements must moreover be so thin that it can easily be replaced, but this significantly reduces the wear resistance.